| 1. |
|
|
| 2. |
|
|
| 3. |
- Ahmadi Naghadeh, Reza, 1982, et al.
(författare)
-
A laboratory characterisation of the response of intact chalk to cyclic loading
- 2022
-
Ingår i: Geotechnique. - : Thomas Telford Ltd.. - 0016-8505 .- 1751-7656. ; In Press
-
Tidskriftsartikel (refereegranskat)abstract
- This paper reports the cyclic behaviour of chalk, which has yet to be studied comprehensively. Multiple undrained high-resolution cyclic triaxial experiments on low- to medium-density intact chalk, along with index and monotonic reference tests, define the conditions under which either thousands of cycles could be applied without any deleterious effect, or failure could be provoked under specified numbers of cycles. Intact chalk's response is shown to differ from that of most saturated soils tested under comparable conditions. While chalk can be reduced to putty by severe two-way displacement-controlled cycling, its behaviour proved stable and nearly linear visco-elastic over much of the one-way, stress-controlled loading space examined, with stiffness improving over thousands of cycles, without loss of undrained shear strength. However, in cases where cyclic failure occurred, the specimens showed little sign of cyclic damage before cracking and movements on discontinuities led to sharp pore pressure reductions, non-uniform displacements and the onset of brittle collapse. Chalk's behaviour resembles the fatigue response of metals, concretes and rocks, where micro-shearing or cracking initiates on imperfections that generate stress concentrations; the experiments identify the key features that must be captured in any representative cyclic loading model.
|
|
| 4. |
- Ahmadi-Naghadeh, Reza, et al.
(författare)
-
A new isotropic specimen preparation method from slurry for both saturated and unsaturated triaxial testing of a low-plasticity silt
- 2019
-
Ingår i: ASTM geotechnical testing journal. - : ASTM International. - 0149-6115 .- 1945-7545. ; 42:4, s. 854-879
-
Tidskriftsartikel (refereegranskat)abstract
- A new procedure for the preparation of low-plasticity silt specimens that are isotropically reconstituted from slurry is developed for use in both saturated and unsaturated soil testing. Spatial variations of the water content and grain size distribution were examined to confirm the uniformity of the specimens (regarding void radio and segregation). The new preparation method results in a homogeneous specimen, which has a simple stress history. The repeatability of the proposed method in preparing identical specimens was verified for both saturated and unsaturated soil testing. The strength and volumetric behavior of specimens prepared by the introduced method are compared with those of moist-tamped compacted specimens and one-dimensionally reconstituted slurry specimens by performing consolidated drained triaxial tests. The microstructure of the specimens prepared with different methods was examined using Scanning Electron Microscopy and Mercury Intrusion Porosimetry. The test results indicate that silt specimens could exhibit either dilative or contractive behavior at normal consolidated conditions, depending on the microstructure.
|
|
| 5. |
- Ahmadi-Naghadeh, Reza, et al.
(författare)
-
Exponential Equation for Predicting Shear Strength Envelope of Unsaturated Soils
- 2019
-
Ingår i: International Journal of Geomechanics. - : American Society of Civil Engineers (ASCE). - 1532-3641 .- 1943-5622. ; 19:7
-
Tidskriftsartikel (refereegranskat)abstract
- An exponential equation is introduced to predict the nonlinear variation of shear strength with matric suction for unsaturated soils. The proposed equation involves three constant parameters, two of which are effective shear strength parameters (i.e., ′ and c′). The third parameter is the maximum capillary cohesion, c″max, which is the maximum possible increase in shear strength due to matric suction. A procedure for the determination of c″max from the soil-water characteristic curve (SWCC) is devised. The proposed equation is validated through a series of constant-suction consolidated drained triaxial tests conducted on specimens reconstituted by isotropic consolidation from the slurry state. In addition, the validity of the equation is investigated by applying it to the test results of five other soils that were available in the literature for the low-suction range (i.e., up to 1,500 kPa). A comparative study on the prediction of shear strength was carried out between the proposed equation and six other shear strength equations found in the literature. The results show that the proposed equation provides reliable predictions of the shear strength of unsaturated soils when the shear strength converges to an asymptotic value at the residual water content.
|
|
| 6. |
- Ahmadi-Naghadeh, Reza, et al.
(författare)
-
Volume change measurement in triaxial tests by monitoring cell fluid volume based on viscoelastic behavior of the test setup
- 2017
-
Ingår i: ASTM geotechnical testing journal. - : ASTM International. - 0149-6115 .- 1945-7545. ; 40:4, s. 683-697
-
Tidskriftsartikel (refereegranskat)abstract
- A novel procedure was developed to measure the total volume change of the unsaturated soils in triaxial testing. The principle of the proposed method was based on cell fluid volume measurements corrected by the assumption of viscoelastic behavior for the triaxial setup. Calibration and parameter determination procedures of the model are devised, and the presented model is implemented into a MATLAB code. The proposed method was validated through a series of consolidated drained triaxial tests on saturated specimens, by comparing the changes in volume measurement of proposed method and conventional measurement (pore fluid). The accuracy in volume measurement during consolidation and shear stages of these tests was between 0.09 and 0.32 cm3, which is on par with or better than more complex and expensive alternatives found in the literature. Repeatability of the proposed technique in measurement of the volume change was also investigated through a series of suction controlled unsaturated soil tests.
|
|
| 7. |
|
|
| 8. |
- Andersson, Roy, et al.
(författare)
-
Similarities and differences between TQM, six sigma and lean
- 2006
-
Ingår i: TQM Magazine. - : Emerald. - 0954-478X .- 1758-6887. ; 18:3, s. 282-296
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Purpose – During the last decades, different quality management concepts, including total quality management (TQM), six sigma and lean, have been applied by many different organisations. Although much important work has been documented regarding TQM, six sigma and lean, a number of questions remain concerning the applicability of these concepts in various organisations and contexts. Hence, the purpose of this paper is to describe the similarities and differences between the concepts, including an evaluation and criticism of each concept.Design/methodology/approach – Within a case study, a literature review and face‐to‐face interviews in typical TQM, six sigma and lean organisations have been carried out.Findings – While TQM, six sigma and lean have many similarities, especially concerning origin, methodologies, tools and effects, they differ in some areas, in particular concerning the main theory, approach and the main criticism. The lean concept is slightly different from TQM and six sigma. However, there is a lot to gain if organisations are able to combine these three concepts, as they are complementary. Six sigma and lean are excellent road‐maps, which could be used one by one or combined, together with the values in TQM.Originality/value – The paper provides guidance to organisations regarding the applicability and properties of quality concepts. Organisations need to work continuously with customer‐orientated activities in order to survive; irrespective of how these activities are labelled. The paper will also serve as a basis for further research in this area, focusing on practical experience of these concepts.
|
|
| 9. |
- Andersson, Roy
(författare)
-
Supply chain resilience through quality management
- 2009
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The length and complexity of the supply chain tend to increase, rather than diminish, thereby making the supply chain riskier and less predictable and, hence, more vulnerable. At the same time, customers are becoming increasingly demanding. The challenge to businesses today is to create a resilient supply chain in order to manage and mitigate risk and vulnerability.The purpose of the thesis is to explore, describe and develop the use of a combined quality management philosophy in logistics processes in order to improve supply chain resilience. The findings are supported by six studies, which are presented here in six papers.The studies show that there is a lot to gain if organisations are able to combine quality management philosophies, as they are complementary to one another. TQM places its strongest emphasis on the commitment and involvement of all employees. Lean is a discipline that focuses on process speed and removal of waste in order to increase customer value. Six Sigma benefits from an added focus on variability and design of products/services and processes. It has been indicated that a combined quality management philosophy makes the logistics processes more reliable, flexible, agile and robust while reducing cost. The companies’ risk awareness has increased and their risk management has been improved, thanks to the Six Sigma training programmes and philosophy. Using a combined quality management philosophy, the speed of production could be increased, and the responsiveness and flexibility could be improved, which means quicker response to changes. It has also been indicated that a combined quality management philosophy improves the companies’ resilience, due to their increased agility and strengthened ability to handle variability and risk management. Quality management tools can be very effective in the companies’ efforts to control supply chain risk and to identify risk sources of variation, even outside the focal company. In Six Sigma projects, the root cause of variation is often found outside the focal companies, which requires more collaboration in the supply chain. However, if the companies that use a combined quality management philosophy intend to become more resilient, they must involve suppliers and customers more in their own processes and design products/services and processes together.Collaboration with the suppliers and customers and the notion of how to extend a combined quality management philosophy outside the focal company are of importance in order to make the whole supply chain resilient. This could lead to a problem, especially since the conditions for transport and logistics in regards to the application of quality methods and tools represent a large area, unexploited by the companies. On the other hand, Six Sigma has standardised training courses, and it has been demonstrated how a Six Sigma framework can enable collaboration across companies’ boundaries in the supply chain, with the use of Six Sigma training and the DMAIC-roadmap as a common platform. Even if a combined quality management philosophy is effective and efficient, the companies must re-invest in additional methods, tools and strategies to make the entire supply chain resilient. It could be this re-investment in risk prevention and mitigation solutions that enables faster process responsiveness, the establishment of a risk management culture by creating common values, culture and rules in the supply chain and the use of logistics strategies and methods.
|
|
| 10. |
- Andersson, Roy, et al.
(författare)
-
Total productive maintenance in support processes : an enabler for operation excellence
- 2015
-
Ingår i: Total Quality Management and Business Excellence. - : Informa UK Limited. - 1478-3363 .- 1478-3371. ; 26:9-10, s. 1042-1055
-
Tidskriftsartikel (refereegranskat)abstract
- In order to stay competitive in today's marketplace, it is vital to reduce activities that do not create value. Lean production has in the last decade been seen as a philosophy to reduce non-value time. The office environment often presents a major improvement opportunity to reduce non-value time. Lean contributes positively to business performance applied in a manufacturing context and is also suggested to do the same in a service context. The purpose of the paper is to analyse and determine how total productive maintenance (TPM) can be applied within the support process and to identify effects from an employee and business perspective. A case study has been performed and a qualitative research approach was selected. Empirical data were gathered by using semi-structured interviews at one case company, but from several teams that had applied TPM. The result was then used as an inductive approach to explore how TPM can be applied in a support process. To implement and apply TPM within an office context, it should be structured in three steps (i) define, (ii) implement and (iii) sustain. TPM should be conducted as a part of the ordinary day-to-day work. The planning and discussions connected to TPM can be included in regular daily departmental stand-up meetings' involving everybody. The work with 5S and maintenance should also be a part of the TPM structure, connecting it as a system and not as an isolated activity. TPM can create value from both a business and an employee perspective. In the employee perspective, TPM reduces the risk of missing/forgetting areas of responsibility and creates more involvement. In the business perspective, objectives such as cost and quality are improved, but TPM also enables the reduction of waste.
|
|
