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Investigation of methods for weld evaluation

Bernhardt, Jean-Patrick LU (2015) In TFHF-2015 FHL820 20142
Solid Mechanics
Abstract
The core business of Sandvik SRP AB are rock crushers. Today Sandvik evaluates the welded joints by simplified and somewhat conservative methods.

The task is to investigate alternative weld evaluation methods.

This have been done by creating different submodels of the area of interest, where the welds is represented in different ways. Different element types have been used, by following recommendations from IIW, in order to get a feel for the pre-processing time and to see how the results varies between the different methods. Finally the stress range is calculated, at the weld toe, by using either the Hot-Spot Stress Method (HSSM) or Effective Notch Stress Method (ENSM).
It should be noted that this thesis will only cover stresses... (More)
The core business of Sandvik SRP AB are rock crushers. Today Sandvik evaluates the welded joints by simplified and somewhat conservative methods.

The task is to investigate alternative weld evaluation methods.

This have been done by creating different submodels of the area of interest, where the welds is represented in different ways. Different element types have been used, by following recommendations from IIW, in order to get a feel for the pre-processing time and to see how the results varies between the different methods. Finally the stress range is calculated, at the weld toe, by using either the Hot-Spot Stress Method (HSSM) or Effective Notch Stress Method (ENSM).
It should be noted that this thesis will only cover stresses at the weld toe.
Two types of welds will be studied, fillet weld and edge fillet weld.
The FE-analysis is done by using the HyperWorks 13.0 suit by Altair Inc.
The work is based on the following industrial standards: BSK07, EC 3 and IIW.

The following configurations have been looked at:
* Shell model using second order 8-node quadratic elements, where the weld stiffness is not taken into account. The stress range is calculated by using the HSSM.
* Shell model using second order 8-node quadratic elements, where the weld stiffness is taken into account by modeling oblique shell elements for the fillet weld and ordinary shell elements for the edge fillet weld. The stress range is calculated by using the HSSM.
* Solid model using second order 10-node tetrahedral elements, where the fillet and edge fillet weld have been included into the model. The stress range is calculated by using the HSSM.
* Solid model using second order 10-node tetrahedral elements, where the fillet and edge fillet weld have been included into the model. The stress range is calculated by using the ENSM.

These models are then compared to Sandvik's model which is modeled with first order 4-node quadratic elements and where the stress range is calculated by using signed von Mises stress.

During the FE-analysis, the subframe was subjected to four loads that were applied in a sequential order, in order to simulate one rotation of the cone crusher.

The stress ranges are then compared towards fatigue classes provided by BSK07, EC3 and IIW.

It has been concluded that the Sandvik approach gives over conservative results compared to the investigated weld evaluation methods. It must also be noted that they use equivalent stress to calculate the stress range, which is not recommend when investigating weld fatigue, according to the studied references.

In the end, the following weld evaluation methods where recommended:
* Shell model using second order 8-node quadratic elements, where the weld stiffness is taken into account by modeling oblique shell elements for the fillet weld and ordinary shell elements for the edge fillet weld. The stress range is calculated by using the HSSM.
* Solid model using second order 10-node tetrahedral elements, where the fillet and edge fillet weld have been included into the model. The stress range is calculated by using the HSSM.

Ethical aspects have not influenced the work of this master's thesis. (Less)
Popular Abstract
In many industries such as the automotive, airplane, shipbuilding and heavy duty machining industries, welding is an important part during the manufacturing process. Methods such as the Nominal stress method, Hot-Spot Stress Method (HSSM), Effective Notch Stress Method (ENSM) and the Linear Elastic Fracture Mechanics Method (LEFM) can be used for evaluating the fatigue life of an weld.
The thesis is done in collaboration with Sandvik SRP AB. The task is to investigate alternative weld evaluation methods, in order to find a calculation and evaluation method that is less conservative and person dependent and at the same time does not prolong the current
pre- and post-processing time. The approach that Sandvik uses to evaluate the fatigue... (More)
In many industries such as the automotive, airplane, shipbuilding and heavy duty machining industries, welding is an important part during the manufacturing process. Methods such as the Nominal stress method, Hot-Spot Stress Method (HSSM), Effective Notch Stress Method (ENSM) and the Linear Elastic Fracture Mechanics Method (LEFM) can be used for evaluating the fatigue life of an weld.
The thesis is done in collaboration with Sandvik SRP AB. The task is to investigate alternative weld evaluation methods, in order to find a calculation and evaluation method that is less conservative and person dependent and at the same time does not prolong the current
pre- and post-processing time. The approach that Sandvik uses to evaluate the fatigue of a weld joint is based on the use of equivalent stresses (signed von Mises). The use of equivalent stresses are not recommended since it is a scalar without a direction. Stresses perpendicular towards a weld have a higher notch action than parallel to the weld. Hence, perpendicular stresses towards the weld toe are more dangerous.
The focus in this thesis have been placed on the HSSM and ENSM, where one have also investigated different ways to model the weld.
One of the limitations in the thesis is that the weld toe stress (the notch that occurs in the transition between the weld and plate) only will be investigated.
The work have been based on the following industrial standards: International Institute of Welding (IIW), Boverkets handbok om stålkonstruktioner (BSK07) and Eurocode 3 - Design of Steel Structures (EC3).

It has been concluded that the Sandvik approach gives over conservative results compared to the investigated weld evaluation methods. It must also be noted that the use of equivalent stresses when calculating the stress range is not recommend, when investigating weld fatigue, according to the studied references. (Less)
Please use this url to cite or link to this publication:
author
Bernhardt, Jean-Patrick LU
supervisor
organization
course
FHL820 20142
year
type
H3 - Professional qualifications (4 Years - )
subject
keywords
Hot-spot stress method, Effective notch stress method, weld, weld joints, evaluation, modeling methods, HyperMesh, HyperView.
publication/series
TFHF-2015
language
English
id
5275165
date added to LUP
2015-07-03 11:02:53
date last changed
2015-07-03 11:02:53
@misc{5275165,
  abstract     = {The core business of Sandvik SRP AB are rock crushers. Today Sandvik evaluates the welded joints by simplified and somewhat conservative methods.

The task is to investigate alternative weld evaluation methods.

This have been done by creating different submodels of the area of interest, where the welds is represented in different ways. Different element types have been used, by following recommendations from IIW, in order to get a feel for the pre-processing time and to see how the results varies between the different methods. Finally the stress range is calculated, at the weld toe, by using either the Hot-Spot Stress Method (HSSM) or Effective Notch Stress Method (ENSM).
It should be noted that this thesis will only cover stresses at the weld toe.
Two types of welds will be studied, fillet weld and edge fillet weld.
The FE-analysis is done by using the HyperWorks 13.0 suit by Altair Inc.
The work is based on the following industrial standards: BSK07, EC 3 and IIW.

The following configurations have been looked at:
* Shell model using second order 8-node quadratic elements, where the weld stiffness is not taken into account. The stress range is calculated by using the HSSM.
* Shell model using second order 8-node quadratic elements, where the weld stiffness is taken into account by modeling oblique shell elements for the fillet weld and ordinary shell elements for the edge fillet weld. The stress range is calculated by using the HSSM.
* Solid model using second order 10-node tetrahedral elements, where the fillet and edge fillet weld have been included into the model. The stress range is calculated by using the HSSM.
* Solid model using second order 10-node tetrahedral elements, where the fillet and edge fillet weld have been included into the model. The stress range is calculated by using the ENSM.

These models are then compared to Sandvik's model which is modeled with first order 4-node quadratic elements and where the stress range is calculated by using signed von Mises stress.

During the FE-analysis, the subframe was subjected to four loads that were applied in a sequential order, in order to simulate one rotation of the cone crusher.

The stress ranges are then compared towards fatigue classes provided by BSK07, EC3 and IIW.

It has been concluded that the Sandvik approach gives over conservative results compared to the investigated weld evaluation methods. It must also be noted that they use equivalent stress to calculate the stress range, which is not recommend when investigating weld fatigue, according to the studied references.
	
In the end, the following weld evaluation methods where recommended:
* Shell model using second order 8-node quadratic elements, where the weld stiffness is taken into account by modeling oblique shell elements for the fillet weld and ordinary shell elements for the edge fillet weld. The stress range is calculated by using the HSSM.
* Solid model using second order 10-node tetrahedral elements, where the fillet and edge fillet weld have been included into the model. The stress range is calculated by using the HSSM.

Ethical aspects have not influenced the work of this master's thesis.},
  author       = {Bernhardt, Jean-Patrick},
  keyword      = {Hot-spot stress method,Effective notch stress method,weld,weld joints,evaluation,modeling methods,HyperMesh,HyperView.},
  language     = {eng},
  note         = {Student Paper},
  series       = {TFHF-2015},
  title        = {Investigation of methods for weld evaluation},
  year         = {2015},
}