The phrase "difficulty in convergence" is correct and usable in written English.
It is typically used to describe a situation which is difficult to resolve due to opposing points of view or interests. For example, "The two sides have had difficulty in convergence regarding the new trade agreement."
This causes jumps in the contact forces due to the discrete nature of the constraint enforcement and difficulties in convergence for implicit solution techniques.
In fitting the generalized log-logistic model to many data sets, we have not experienced any difficulty in obtaining convergence with this technique.
Due to small numbers of diagnoses leading to instability of model estimates and difficulty in model convergence, models were only built for ICD-10 categories achiving >15 monthly consults, and mental health staffing variables were excluded for all ICD-10 diagnostic categories, save schizophrenia/delusional disorders and epilepsy.
For this type of data, the model has difficulty in parameter convergence for small values of λ, reflecting the fact that the multivariate data distribution is too noisy for nonparametric part of the model to work alone; thus a parametric unimodal component is needed to help cluster the data.
However, it is important for the reader to be aware why the low turgor choice was made, the difficulties in model convergence in such a system, and the issue with anticlinal walls.
First, despite the difficulty in proving the convergence of full IFEM algorithms, both IFEM-1 and IFEM-2 are always observed to converge.
The major difficulty in studying the convergence of the dynamics of these two cases is that prices will change over time with migration flows so that an individual must anticipate all possible movements prior to make the decision to migrate and return migrate.
A simplified spudcan, with its side friction ignored because of its relative smaller area, is adopted to reduce the difficulty of convergence in calculation.
A particular difficulty however is the decrease in convergence rate associated with the increase in number of solution domains.
The geometrical and contact nonlinearities in tubular buckling problem lead to convergence difficulty in calculation.
