A medical device company has drafted the following excerpt from a Failure Mode Effect Analysis (FMEA)....

 

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A medical device company has drafted the following excerpt from a Failure Mode Effect Analysis (FMEA). The FMEA was completed to a draft stage and was awaiting the results of the fatigue tests highlighted in column 8 of the FMEA, prior to reaching an approved document, However, on completion of the mechanical fatigue testing programme, 40% of the Nitinol frame specimens failed prior to the expected lifetime of 200 million cycles, and subsequently the component was deemed not to pass this risk control measure. Flaws of 300μm were found to exist in the Nitinol frame. The medical device company has three options: (1) Change the specifications of the nitinol alloy to "NEW SPEC NITI" ensuring that the probability of a flaw size greater than 100μm is minimal after the manufacturing process. (10) (iii) Change the material to "Titanium" that has flaw sizes of Sum Continue to use the original nitinol material but use a new quality control inspection procedure to eliminate all the specimens with flaws of a length greater than 20μm. The implication of each change from an economic perspective is: "NEW SPEC NITI" will add €25 per device The "titanium" component will add €55 per device The direct cost of the new quality control procedure is €50,000 to install, this is a one off payment. Plus the cost of removing all the below quality devices from the production line. Table Q3 DRAFT excerpt from a Failure Mode Effect Analysis for a new atrial Septal Defect (ASD) repair device Component Potential part Potential effect of Severity Potential Cause of failure mode Occurrence Current risk controls (0) Failure (S) Mode failure mode Migration of 5 Nitinol frame Fracture of the strut the fractured strut to a blood vessel in the brain causing death Insufficient material fatigue strength 2 MEP56BM9-901 Page 6 of 8 Finite element analysis supports 10 year fatigue life data with safety factors between 1.7 and 4. Fatigue tests support 200 million cycles of fatigue life (AWAITING RESULTS) Detection RPN (D) 2 4 40 The following relationships exist between stress intensity and fatigue crack growth, applied stress range and crack length: Whereby: a is the crack length in metres da dN = C(AK) ΔΚ = QΔσνπα Failure is considered if a crack reaches a total length of 700μm N is the number of cycles m = 3.3 and C= 1.0x10 12 for the original Nitinol material m = 3, and C= 1.9x10-¹1 for the new spec NiTi material m = 2.5, and C= 5.2 x 10-¹2 for the titanium material Q is a constant and is 1.2 in this scenario Ao constant and is equal to 80MPa (ii) The expected life of the device is 200 million cycles. MEP56BM9-901 (1)Choose the most appropriate option to move forward with based on a fatigue crack growth analysis and the economics of the situation, justify your answer. [20 marks] Why may this analysis not be quite correct? [5 marks] Page 7 of 8 A medical device company has drafted the following excerpt from a Failure Mode Effect Analysis (FMEA). The FMEA was completed to a draft stage and was awaiting the results of the fatigue tests highlighted in column 8 of the FMEA, prior to reaching an approved document, However, on completion of the mechanical fatigue testing programme, 40% of the Nitinol frame specimens failed prior to the expected lifetime of 200 million cycles, and subsequently the component was deemed not to pass this risk control measure. Flaws of 300μm were found to exist in the Nitinol frame. The medical device company has three options: (1) Change the specifications of the nitinol alloy to "NEW SPEC NITI" ensuring that the probability of a flaw size greater than 100μm is minimal after the manufacturing process. (10) (iii) Change the material to "Titanium" that has flaw sizes of Sum Continue to use the original nitinol material but use a new quality control inspection procedure to eliminate all the specimens with flaws of a length greater than 20μm. The implication of each change from an economic perspective is: "NEW SPEC NITI" will add €25 per device The "titanium" component will add €55 per device The direct cost of the new quality control procedure is €50,000 to install, this is a one off payment. Plus the cost of removing all the below quality devices from the production line. Table Q3 DRAFT excerpt from a Failure Mode Effect Analysis for a new atrial Septal Defect (ASD) repair device Component Potential part Potential effect of Severity Potential Cause of failure mode Occurrence Current risk controls (0) Failure (S) Mode failure mode Migration of 5 Nitinol frame Fracture of the strut the fractured strut to a blood vessel in the brain causing death Insufficient material fatigue strength 2 MEP56BM9-901 Page 6 of 8 Finite element analysis supports 10 year fatigue life data with safety factors between 1.7 and 4. Fatigue tests support 200 million cycles of fatigue life (AWAITING RESULTS) Detection RPN (D) 2 4 40 The following relationships exist between stress intensity and fatigue crack growth, applied stress range and crack length: Whereby: a is the crack length in metres da dN = C(AK) ΔΚ = QΔσνπα Failure is considered if a crack reaches a total length of 700μm N is the number of cycles m = 3.3 and C= 1.0x10 12 for the original Nitinol material m = 3, and C= 1.9x10-¹1 for the new spec NiTi material m = 2.5, and C= 5.2 x 10-¹2 for the titanium material Q is a constant and is 1.2 in this scenario Ao constant and is equal to 80MPa (ii) The expected life of the device is 200 million cycles. MEP56BM9-901 (1)Choose the most appropriate option to move forward with based on a fatigue crack growth analysis and the economics of the situation, justify your answer. [20 marks] Why may this analysis not be quite correct? [5 marks] Page 7 of 8

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1 Based on the fatigue crack growth analysis and economics the most appropriate option to move forwa... View the full answer