Mechanical Failure Analysis Storytelling

“I have a broken bolt that experienced failure and would like to have it tested. How do you determine what happened?” 

We often receive RFQs similar to the above nature, which have an obvious query but an ambiguous request. Unlike other tests performed here at im体育APP, mechanical 失效分析 requires a different approach – the nature of its existence relies on story building. In our previous blog post, we describe three benefits of performing 失效分析. 对于这个, we’ll focus on the first benefit of root cause determination, how im体育APP approaches these types of analyses, and what the client can do to minimize stories that leave room for interpretation. 

Some stories are short and simple—they have a beginning, middle, and end. Others are like suspense novels – complex plots, 多个字符, 许多系列事件, and sometimes may lack “The End”. When we receive an initial RFQ for 失效分析, we have basic questions that will help us determine how complex the story is. 这些包括:

1. 字符

a. Description (and pictures or videos!) of the part, interfacing parts, and overall machine/instrument.
b. Intended service life of the part vs. 实际生活.
c. Type of material and process/manufacturing background.

2. 设置

a. In what environment did the failure occur? (Conditions, loads, temperature, usage, cycling, pressure, chemical contact, lubricants)
b. Is the part on-site or is it at a customer’s site?

3. 情节

a. Describe any events leading up to the incident (changes in manufacturer or manufacturing process, 材料的变化, is it the first failure of its kind, 或者是持续的失败?).

b. List any observations such as isolated events (lot numbers, locations, specific uses). 

At this point, the story is only half finished, and that’s where im体育APP comes in. Our engineering team will request both the failed part, whether it be a 螺栓、紧固件或螺钉, and a new or unused one for comparison, along with any interfacing parts needed to fit pieces together. 有了这些信息, we’ll then be able to determine the most efficient approach to determining what happened. Oftentimes, we can’t rely on one standard way to go about the investigation. With a gambit of tests at our disposal, running different combinations of tests (which can be few or many) will help us provide the unknown part of the story:
  

4. 冲突

a. Macroscopic examinations of all fracture surfaces and identify any anomalies while noting all observations (lower magnifications). Typically from this type of examination, we get an overview of what type of failure occurred and see what the rest of the parts look like. E.g.视觉描述符.

b. 显微镜观察的考试 of all fracture surfaces for more in-depth examination (higher magnifications). This helps to clarify what macroscopy can’t tell us. We scan surfaces by SEM to further determine the type of failure and note any microscopic anomalies as well. If there are contaminants on either the surface or clearly seen within the fracture, we can run a chemical ID by EDS as well.

c. 硬度测试 of the surface or cross-section core. A quick method to determine material flaws (wrong material), insufficient processing (improper tempering or lack of homogeneity), or get an idea of the material strength.

Depending on what can be gathered from the above inspections, we can generally break down the likely cause of failure to be a material flaw, 制造缺陷, 或者使用不当. While we don’t want to point out the obvious, we want to eliminate any possible causes of failure as deemed necessary. Since im体育APP is known for “breaking stuff” and we have a hunch toward one particular cause, we’ll ask for the go-ahead on part destruction. 然后, we’ll perform a microscopic evaluation to confirm microstructures, 锻造缺陷, 内部或次生裂缝, 等.

As a third-party testing laboratory, im体育APP approaches mechanical failure analyses unbiasedly. The success of a 失效分析 depends largely on the build-up of the plot; however with insufficient plot development, only the ending – the failure of the fastener - is known for sure.

To learn more about mechanical 失效分析, or if you have any questions, 今天就im体育APP的团队.