PSI - Issue 14

2 2 2 2 2 2 2 2 2

Nevil Martin Jose et al. / Procedia Structural Integrity 14 (2019) 403–409 Nevil Martin Jose et.al/ Structural Integrity Procedia 00 (2018) 000–000 Nevil Martin Jose et.al/ Structural Integrity Procedia 00 (2018) 000–000 Nevil Martin Jose et.al/ Structural Integrity Procedia 00 (2018) 000–000 Nevil artin Jose et.al/ Structural Integrity Procedia 00 (2018) 000–000 Nevil Martin Jose et.al/ Structural Integrity Procedia 00 (2018) 000–000 Nevil Martin Jose et.al/ Structural Integrity Procedia 00 (2018) 000–000 Nevil Martin Jose et.al/ Structural Integrity Procedia 00 (2018) 000–000 Nevil Martin Jose et.al/ Structural Integrity Procedia 00 (2018) 000–000 Nevil Martin Jose et.al/ Structural Integrity Procedia 00 (2018) 000–000

Email: nevil@barc.gov.in 1. Introduction Email: nevil@barc.gov.in 1. Introduction Email: nevil@barc.gov.in 1. Introduction Email: nevil@barc.gov.in 1. Introduction Email: nevil@barc.gov.in 1. Introduction Email: nevil@barc.gov.in 1. Introduction Email: nevil@barc.gov.in 1. Introductio Email: nevil@barc.gov.in 1. Introduction Email: nevil@barc.gov.in 1. Introduction

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Master curve approach, is a fracture mechanics based approach used to obtain the fracture toughness of ferritic steels in the ductile to brittle transition temperature (DBTT) region. Master curve approach has been developed at VTT manufacturing technology by Kim Wallin et.al. (2001). Master curve is based on the property of ferritic steels that in the DBTT region, their fracture toughness follows a characteristic statistical distribution. In the master curve approach, fracture tests are conducted at a temperature range expected to be in the DBTT region. This expected test temperature may be obtained through Charpy impact tests, as explained in D. McCabe et.al. (2005). The fracture tests then conducted at this temperature, as described in ASTM E1921 gives the reference temperature T 0 . The reference temperature T 0 can then be used for obtaining the fracture toughness curve named as the master curve, in the DBTT region. Reactor pressure vessel (RPV), which are made of low alloy ferritic steels, needs to be ensured that under all operating conditions, is above the DBTT region. This ensures the structural integrity of the RPV by avoiding chances for brittle fracture. Irradiation of ferritic steels shifts the DBTT region to higher temperatures. So, the fracture toughness of RPV steels must be obtained at periodic intervals as the current DBTT region is dependent on the current irradiation level. This requires carrying out master curve experiments at periodic intervals. Specimens known as surveillance specimens which are made of same material as RPV are put inside the RPV from the start so that the irradiation damage levels of the specimens are same as that of the RPV at any time. So, to obtain the DBTT region of RPV at any time, these specimens can be tested. However, to carryout tests as mentioned in the standards like ASTM E1921, the existing practise is to use specimens of relatively larger sizes. However, the space available inside RPV to keep surveillance specimens are limited. Also, irradiation doses associated with testing these specimens are more. If miniaturised specimens can be used for testing, these two problems can be reduced. In the literature, master curve generation from miniature specimens has been carried out by different researchers. For example, Masato Yamamato et.al. (2014) have carried out experiments to obtain master curve from miniature CT specimens. In this work, the applicability of using miniature CT specimens to determine the master curve of 20MnMoNi55 steel is investigated. 2. Experimental details The material used for the present study is 20MnMoNi55 steel. This is a low alloy ferritic steel. Miniature CT specimens of dimensions shown in Fig. 1 has been used for the experiment. These specimens are similar to that had been used by Masato Yamamoto et.al. (2014). Master curve approach, is a fracture mechanics based approach used to obtain the fracture toughness of ferritic steels in the ductile to brittle transition temperature (DBTT) region. Master curve approach has been developed at VTT manufacturing technology by Kim Wallin et.al. (2001). Master curve is based on the property of ferritic steels that in the DBTT region, their fracture toughness follows a characteristic statistical distribution. In the master curve approach, fracture tests are conducted at a temperature range expected to be in the DBTT region. This expected test temperature may be obtained through Charpy impact tests, as explained in D. McCabe et.al. (2005). The fracture tests then conducted at this temperature, as described in ASTM E1921 gives the reference temperature T 0 . The reference temperature T 0 can then be used for obtaining the fracture toughness curve named as the master curve, in the DBTT region. Reactor pressure vessel (RPV), which are made of low alloy ferritic steels, needs to be ensured that under all operating conditions, is above the DBTT region. This ensures the structural integrity of the RPV by avoiding chances for brittle fracture. Irradiation of ferritic steels shifts the DBTT region to higher temperatures. So, the fracture toughness of RPV steels must be obtained at periodic intervals as the current DBTT region is dependent on the current irradiation level. This requires carrying out master curve experiments at periodic intervals. Specimens known as surveillance specimens which are made of same material as RPV are put inside the RPV from the start so that the irradiation damage levels of the specimens are same as that of the RPV at any time. So, to obtain the DBTT region of RPV at any time, these specimens can be tested. However, to carryout tests as mentioned in the standards like ASTM E1921, the existing practise is to use specimens of relatively larger sizes. However, the space available inside RPV to keep surveillance specimens are limited. Also, irradiation doses associated with testing these specimens are more. If miniaturised specimens can be used for testing, these two problems can be reduced. In the literature, master curve generation from miniature specimens has been carried out by different researchers. For example, Masato Yamamato et.al. (2014) have carried out experiments to obtain master curve from miniature CT specimens. In this work, the applicability of using miniature CT specimens to determine the master curve of 20MnMoNi55 steel is investigated. 2. Experimental details The material used for the present study is 20MnMoNi55 steel. This is a low alloy ferritic steel. Miniature CT specimens of dimensions shown in Fig. 1 has been used for the experiment. These specimens are similar to that had been used by Masato Yamamoto et.al. (2014). Master curve approach, is a fracture mechanics based approach used to obtain the fracture toughness of ferritic steels in the ductile to brittle transition temperature (DBTT) region. Master curve approach has been developed at VTT manufacturing technology by Kim Wallin et.al. (2001). Master curve is b sed on the property of ferritic steels that in the DBTT region, their fracture toughness follows a characteristic statistical distribution. In the master curve approach, fracture tests are conducted at a temperature range expected to be in the DBTT region. This expected test temperature may be obtained through Charpy impact tests, as explained in D. McCabe et.al. (2005). The f acture tests then onduct d at this temperature, a described in ASTM E1921 gives the reference temperature T 0 . The reference temperature T 0 can then be used for obtaining the fracture toughness curve named as the master curve, in the DBTT region. Rea tor pressure vessel (RPV), which are made of low alloy ferritic steels, needs to be ensured that under all operating conditions, is above the DBTT region. This ensures the structural integrity of the RPV by avoiding chances for brittle fracture. Irradiation of ferritic steels shifts the DBTT region to higher temperatures. So, the fracture toughness of RPV steels must be obtained at periodic intervals as the current DBTT region is dependent on the current irradiation level. This requires carrying out master curve experiments at periodic intervals. Specimens known as surveillance specimens which are made of same aterial as RPV are put inside the RPV from the start so that the irradiation damage levels of the specimens are same as that of the RPV at any time. So, to obtain t e DBTT region of RPV at any time, these specimens can be tested. However, to carryout te ts as mentioned in the standards like ASTM E1921, th existing practise is to use spec mens of relatively l rger sizes. However, the space available ins de RPV to keep surveillance specimens are limited. Also, irradiation doses associated with testing these spec mens are more. If miniaturised speci ens c n be used for testing, these two pro lems can be reduced. In the literature, mas er curve generation from miniatu e specimens has been carried out by different researchers. For example, Masato Yamama o et.al. (2014) have carried out experiments to obtain master curve from miniature CT specimens. In this work, the applicability of using miniature CT specimens to determine the master curve of 20MnMoNi55 steel is investigated. 2. Experimental details The mater al used for t e present study is 20MnMoNi55 steel. This is a low alloy ferritic steel. Miniature CT specim s of imensions shown in Fig. 1 has been used for the experiment. These specimens are similar to that had been used by Masato Yamamoto et.al. (2014). Master curve approach, is a fracture mechanics based approach used to obtain the fracture toughness of ferritic steels in the ductile to brittle transition temperature (DBTT) region. Master curve approach has been developed at VTT manufacturing technology by Kim Wallin et.al. (2001). Master curve is b sed on the property of ferritic st els that in the DBTT region, their fracture toughness follows a characteristic statistical distribution. In the master curve approach, fr cture tests are co ducted at a temperature range expected to be in the DBTT region. This expected test temperature may be obtained through Charpy impact tests, as explained in D. McCabe et.al. (2005). The f acture tests then onducted at this temperature, a escribed in ASTM E1921 gives the reference t mperature T 0 . The reference temperature T 0 can then be used for obtaining the fracture toughness curve named as the master curve, in the DBTT region. Rea t r pressure vessel (RPV), which are made of low alloy ferritic steels, needs to be ensured that under all operating conditions, is above the DBTT region. This ensures the structural integrity of the RPV by avoiding chances for brittle fracture. Irradiation of ferritic steels shifts the DBTT region to higher temperatures. So, the fracture toughness of RPV steels must be obtained at periodic intervals as the current DBTT region is dependent on the current irradiation level. This requires carrying out master curve experiments at periodic intervals. Specimens known as surveillance specimens which are made of same aterial as RPV are put inside the RPV from the start so that the irradiation damage levels of the specimens are same as that of the RPV at any time. So, to obtain the DBTT region of RPV at any time, these specimens can be tested. However, to carryout te ts as mentioned in the standards like ASTM E1921, th existing practise is to use spec mens of relatively l rger sizes. However, the space available inside RPV to keep surve llance specimens are limited. Also, irradiation doses associated with testing these specimens are more. If miniaturised speci ens c n be used for testing, these two problems can be reduced. In the literature, mas er curve generation from miniatu e specimens has been carried out by different researchers. For example, Masato Yamamato et.al. (2014) have carried out experiments to obtain master curve from miniature CT specimens. In this work, the applicability of using miniature CT specimens to determine the master curve of 20MnMoNi55 steel is investigated. 2. Experimental details The mater al used for t e present study is 20MnMoNi55 steel. This is a low alloy ferritic steel. Miniature CT specim s of imensions shown in Fig. 1 has been used for the experiment. These specimens are similar to that had been used by Masato Yamamoto et.al. (2014). Master curve approach, is a fracture mechanics based approach used to obtain the fracture toughness of ferritic steels in the ductile to brittle transition temperature (DBTT) region. Master curve approach has been developed at VTT m nufacturing technology by Kim Wallin et.al. (2001). Master curve is based on the property of ferritic steels that in the DBTT region, their fracture toughness follows a charact risti statistical distribution. In the master curve approach, fr cture tests are conducted at a temperature range expected to be in the DBTT region. This expected test temperature may be obt ined through Charpy impact tests, as explained in D. McCabe et.al. (2005). The fracture tests then conducted at this temperature, as described in ASTM E1921 gives the reference temperature T 0 . The reference temperature T 0 can then be used for obtaining the fracture toughness curve named as the master curve, in the DBTT region. Reactor pressure vessel (RPV), which are made of low alloy ferritic steels, needs to be ensured that under all operating conditions, is above the DBTT region. This ensures the structural integrity of the RPV by avoiding chances for brittle fracture. Irradiation of ferritic steels shifts the DBTT region to high r temperatures. So, the fracture toughness of RPV steels must be obtained at periodic intervals as the current DBTT region is dependent on the current irradiation level. This requires carrying out mast r curve experiments at periodic intervals. Specimens known as surveillance specimens which are made of same material as RPV are put inside the RPV from the start so that the irradiation damage l vels of th specimens ar ame as that of the RPV t any time. So, to obtain the DBTT region of RPV at any time, these specimens an be tested. However, to carryout te ts a mention d in t e standards like ASTM E1921, the existi g practise is to use specim ns of relatively l rger sizes. However, the space available inside RPV to keep surveillance specimens are limited. Also, irradiation dos s associated with t ting these specimens are mor . If mini turised speci ens can be used for testing, these two problems can be reduced. In the lit rature, master curve gener tion from miniature specimens has been carried out by differ nt res archers. For example, Ma ato Yamamato et.al. (2014) have carried out experiments to obtain master curve from miniature CT specimens. In this work, the applicability of using miniature CT specimens to determine the master curve of 20MnMoNi55 steel is investigated. 2. Experimental details The material used for the present study i 20MnMoNi55 st el. This is a low alloy f rritic steel. Miniature CT specimens of dimensions shown in Fig. 1 has been used for the experiment. These specimens are similar to that had been used by Masato Yamamoto et.al. (2014). M ster curve approach, is a fracture mechanics based approach used to obtain the fracture toughness of ferritic steels in the ductile to brittle transition temperature (DBTT) region. Master curve approach has been developed at VTT m nufacturing technology by Kim Wallin et.al. (2001). Master curve is based on the property of ferritic teels that in the DBTT region, their fracture oughness follows a charact ri ti st t stical distribution. In the master curve approach, fr cture tests are conducted at a temperature range expected to be in the DBTT region. This expec ed test temperature may be obtained through Charpy impact tests, as explained in D. McCab et.al. (2005). The fracture tests then onducted at this temperature, as described in ASTM E1921 gives the refer nce temperature T 0 . The reference temperature T 0 can then be used for obtaining the fracture toughness curve named as the master curve, in the DBTT region. Reactor pressure vessel (RPV), which are made of low alloy ferritic steels, needs to be ensured that under all operating conditions, is above the DBTT region. This ensures the struc ural integrity of the RPV by avoiding chances for brittle fracture. Irradiation of ferritic steels shifts the DBTT region to high r temperatures. So, the fracture toughness of RPV steels must be obtained at periodic intervals as the current DBTT region is dependent on the current irradiation level. This requires carrying out master curve experiments at periodic intervals. Specimens known as surveillance spec ns which are made of sam aterial as RPV are put inside the RPV from the start so that the irradiation damage l vels of th specimens ar ame as that of the RPV t any t me So, to obtain the DBTT region of RPV at any time, these specimens an be tested. However, to carryout te ts a mention d in t e standards like ASTM E1921, th exist g pra ti e is to use sp c ns of relatively l rg r sizes. However, the space available insid RPV to keep surve llanc specimens are limited. Also, irradiation dos s associated with testing these specimens are mor . If mini turised speci ens can b used for testing, these wo problems can be reduced. In the literature, master curve gen r tion from miniature spec mens has been carried ou by different res archers. For example, Ma ato Yamamato et.al. (2014) have carried out experiments to obtain master curve from miniature CT specimens. In this work, the applicability of using miniature CT specimens to determine the master curve of 20MnMoNi55 steel is investigated. 2. Experi ental details The material used for the present s udy is 20MnMoNi55 steel. This is a low alloy ferritic steel. Miniature CT specimens of dimensions shown in Fig. 1 has been used for the experiment. These specimens are similar to that had been used by Masato Yamamoto et.al. (2014). Master curve approach, is a fracture mechanics bas d approach used to obtain the fracture toughness of ferritic steels in the ductile to brittle transition temperature (DBTT) region. Master curve approach has been dev loped at VTT manufacturing technology by Kim Wallin et.al. (2001). Master cu ve is b sed on the property of ferritic steels that in the DBTT region, their fracture toughness follows a characteristic statistical distribution. In the master curve approach, fracture tests are conducted at a temperature range expected to be in the DBTT region. This expected test temperature may be obtained through Charpy impact tests, as explained in D. McCabe et.al. (2005). The fracture tests then conducted at this temperature, as described in ASTM E1921 gives the refer nce temperature T 0 . The reference temperature T 0 can then be used for obtaining the fracture tough ess curve n m d as the master curve, in the DBTT region. Reactor pressure vessel (RPV), which are made of low alloy ferritic steels, needs to be ensured that under all operating conditions, is above the DBTT region. This ensures the structural integrity of the RPV by avoiding chances for brittle fracture. Irradiation of ferritic steels shifts the DBTT region to higher temperatures. So, the fracture toughness of RPV steels must be obtained at periodic intervals as the current DBTT region is dependent on the current irradiation level. This requires carrying out master urve experiments at periodic intervals. Specimens known as surveillance specimens which are made of same aterial as RPV are put inside the RPV from the start so that the irradiation damage l vels of th specimens are same as that of the RPV at any time. So, to obtain the DBTT region of RPV at any time, these specimens can be tested. However, to carryout tests as mentioned in the standards like ASTM E1921, the existing practise is to use specimens of relatively l rger sizes. However, the space available inside RPV to keep surveillance specimens are limited. Also, irradiation doses associated with testing these specimens are mor . If miniaturised specimens can be used for testing, these tw problems can be reduced. In the literature, mas er curve generation from miniature specimens has been carried out by different researchers. For example, Masato Yamamato et.al. (2014) have carried out experiments to obtain master curve from miniature CT specimens. In this work, the applicability of using miniature CT specimens to determine the mast r curve of 20MnMoNi55 steel is investigated. 2. Experi ental details The material used for the present study is 20MnMoNi55 steel. This is a low alloy ferritic steel. Mini ture CT specimens of dimensions shown in Fig. 1 has been used for the experiment. These specimens are similar to that had been used by Masato Yamamoto et.al. (2014). M ster curve approach, is a fracture mechanics bas d appr ach used to obtain the fracture toughness of ferritic steels in the ductile to brittle transition temp rat re (DBTT) region. Master curve approach has been developed at VTT manufacturing technology by Kim Wallin et.al. (2001). Master curve is based on the property of ferritic ste ls that in the DBTT region, their frac ure toughness follows a characteristi statistical distribution. In the master curve approach, fracture tests are conducted at a temperature range expected to be in the DBTT region. This expected test temperature may be obtained through Charpy impact tests, as explained in D. McCabe et.al. (2005). The f acture tests then conducted at this temperature, as described in ASTM E1921 gives the refere ce temperature T 0 . The reference temperature T 0 can then be used for obtaining the fracture toughness curve named as the master curve, in the DBTT region. Reactor pressure vess l (RPV), which are made of low alloy ferritic steels, needs to be ensured that under all operating conditions, is above the DBTT region. This ensures the structu al int grity of the RPV by avoiding chances for brittle fracture. Irradiation of ferritic steels shifts the DBTT region to higher temperatures. So, the fracture toughness of RPV steels must be obtained at periodic intervals as the current DBTT region is dependent on the current irradiation level. This requires carrying out master curve experiments at periodic intervals. Specimens known as surveillance specimens which are made of same material as RPV are put inside the RPV from t e tart so that the irradiation damage levels of the specimens ar same as hat of the RPV at any time. So, to obtain the DBTT region of RPV at any time, these specimens can be tested. However, to carryout tests as mentioned in the standards like ASTM E1921, the existing practise is to use specimens of relatively larger sizes. However, th space available ins de RPV to keep surve llance specimens are limited. Also, irradiation doses associated with testing thes spec mens are more. If miniaturised specimens can be used for testing, these tw problems can be reduced. In the literature, master curve generation from miniature specimens has been carried out by different researchers. For example, Masato Yamamato et.al. (2014) have carried out experiments to obtain master curve from miniature CT specimens. In this work, the applicability of using miniature CT specimens to determine the master curve f 20MnMoNi55 steel is investigated. 2. Experimental details The material used for the present study is 20MnMoNi55 steel. This is a low alloy ferritic steel. Mini ture CT specimens of dimensions shown in Fig. 1 has been used for the experiment. These specimens are similar to that had been used by Masato Yamamoto et.al. (2014). M ster curve approach, is a fractur mechanics based approach us d to obtain the fracture toughness of f rritic steels in th ductil to brittle transition temperat re (DBTT) region. Mast r curve approach has been developed at VTT m nufacturing technology by Kim Wallin et.al. (2001). Master curve is based on the property of ferritic ste ls that in the DBTT r gion, their fracture oughness follows a characteri tic stat sti al distribution. In the master curve pproach, fracture tests are conducted at a temperature range expected to be in the DBTT gion. This expec ed test temp rature may be obtain d throug Charpy impact tes s, as explained in D. McCabe et.al. (2005). The fracture tests then onducted at this temperature, a described in ASTM E1921 gives the reference temperature T 0 . The reference temperature T 0 can then be used for obtaining the fracture toughness curve nam d as the mast r curve, in the DBTT region. Reactor pressure vessel (RPV), which are made of low alloy ferritic steels, needs to be ensured that under all operating conditions, is above the DBTT region. This ensur s the struc ural int grity of the RPV by avoiding chances for br ttle fracture. Irradiation of ferritic steels shifts he DBTT region to higher temperatures. So, th fracture toughness of RPV steels must be obtained at periodic intervals as the current DBTT r gion is dependent on the current irradiation level. This requires carrying out mast r curve experiments at periodic intervals. Specimens known as surveillance specim n which are made of sam material as RPV are put inside the RPV from t start so that the irradiation damage levels of the sp cim ns ar ame as that of the RPV t any t me S , to obtain the DBTT region of RPV at any time, these specimens can be tested. However, to c rryout tests a mentioned in the standards like ASTM E1921, the existing practise is to use specimens of relatively l rger sizes. However, the space available inside RPV to keep surveillance specimens are limited. Also, irradiation dos s associated with t ting th s spec mens are more. If minia urised specimens can be used for testing, these tw problems can be reduced. In the literature, mas er curve gener tion from miniatu e spec mens has been carried out by different res archers. For example, Ma ato Yamama o et.al. (2014) have carried out experiments to obtain master curve from miniature CT specimens. In this work, the applicability of using miniature CT specimens to determine the master curve of 20MnMoNi55 steel is investigated. 2. Experi ntal details The material used for the present s udy i 20MnMoNi55 st el. This is a low alloy ferritic steel. Miniature CT specim s of dimensions shown in Fig. 1 has been used for the experiment. These specimens are similar to that had been used by Masato Yamamoto et.al. (2014).

Fig. 1 Dimensions of MINI-CT specimen The dimensions of the specimens are proportional as per ASTM E1921 standard. The experiments have been carried out on Dynamic Mechanical Analyser machine which can do both static loading and dynamic loading. Before carrying out the tests, the specimen surface was given a mirror finish by polishing using diamond paste having grit size 1µm. This is required to measure crack size during fatigue pre-cracking using optical methods. The experiment consisted of the steps explained below. Fig. 1 Dimensions of MINI-CT specimen The dimensions of the specimens are proportional as per ASTM E1921 standard. The experiments have been carried out on Dynamic Mechanical Analyser machine which can do both static loading and dynamic loading. Before carrying out the tests, the specimen surface was given a mirror finish by polishing using diamond paste having grit size 1µm. This is required to measure crack size during fatigue pre-cracking using optical methods. The experiment consisted of the steps explained below. Fig. 1 Dimensions of MINI-CT specimen The dimensions of the specimens are proportional as per ASTM E1921 standard. The experiments have been carried out o Dynamic Mechanical Analyser machine which can d both static l ading and dynamic loading. Before carry ng out the tests, the specimen surface was given a mirror finish by polishing using diamond paste having grit size 1µm. This is r quired to measure crack size during fatigue pre-cracking using optical methods. The experiment consisted of the steps explained below. Fig. 1 Dimensions of MINI-CT specimen The dimensions of the specimens are proportional as per ASTM E1921 standard. The experiments have been carried out o Dynamic Mechanical Analyser machine which can d both static l ading and dynamic loading. Before carrying out the tests, the specimen surface was given a mirror finish by polishing using diamond paste having grit size 1µm. This is required to measure crack size during fatigue pre-cracking using optical methods. The experiment consisted of the steps explained below. Fig. 1 Dimensions of MINI-CT specimen The dimensions of the specime s are proportional as per ASTM E1921 standard. The experiments have been carried out o Dynamic Mechanical Analyser machine which can do both static loading and dynamic loading. Before carrying out the tests, the specimen surface was giv n a mirror finish by polishing using diamond paste having grit size 1µm. This is required to measure crack size during fatigue pre-cracking using optical methods. The experiment consisted of the steps explained below. Fig. 1 Dimensions of MINI-CT specimen The dimensions of the specime s are proportional as per ASTM E1921 standard. T e experiments have been carr ed out on Dynamic Mechanical Analyser machine which can do both static loading and dynamic loading. Before carrying out the tests, the specimen surface was given a mirror finish by polishing using diamond paste having grit size 1µm. This is required to measure crack size during fatigue pre-cracking using optical methods. The experiment consisted of the steps explained below. Fig. 1 Dimensions of MINI-CT specimen The dimensions of the specimens are proportional as per ASTM E1921 standard. The experiments have been carried out on Dynamic Mechanical Analyser machine which can d both static l ading and dynamic loading. Before carrying out the tests, the specimen surface was given a mirror finish by polishing using diamond paste having grit size 1µm. This is required to measure crack size during fatigue pre-cracking using optical methods. The experiment consisted of the steps explained below. Fig. 1 Dimensions of MINI-CT specimen The dimensions of the specimens are proportional as per ASTM E1921 standard. The experiments have been carri d out on Dynamic Mechanical Analyser machine which can do both static l ading and dynamic loading. Before carry ng out the tests, the specimen surface was given a mirror finish by polishing using diamond paste having grit size 1µm. This is required to measure crack size during fatigue pre-cracking using optical methods. Fig. 1 Dimensions of MINI-CT specimen The dimensio s f the specimens are proportional as per ASTM E1921 standard. The experiments have been c rr ed out on Dynamic Mechanical Analyser machine which ca do both static loading and dynamic loading Before carry ng out the tests, the sp cimen surface was given a mirror finish by polishing using diamond paste having grit size 1µm. This is required to measure crack size during fatigue pre-cracking using optical methods.